Summary Of Significant Accounting Policies (Narrative) (Details)		12 Months Ended
	Apr. 20, 2016	Dec. 31, 2017
Summary of Significant Accounting Policies [Line Items]
Common stock split conversion ratio (2:1)	2
Scenario, Forecast [Member] | Electric Generation [Member] | WPL [Member]
Summary of Significant Accounting Policies [Line Items]
Average rate of depreciation		3.20%
Scenario, Forecast [Member] | Electric Distribution [Member] | WPL [Member]
Summary of Significant Accounting Policies [Line Items]
Average rate of depreciation		2.60%
Scenario, Forecast [Member] | Gas Transmission [Member] | WPL [Member]
Summary of Significant Accounting Policies [Line Items]
Average rate of depreciation		2.30%